1. Field of the Invention
The present invention is generally related to a color printing apparatus, or a color printing system, and more specifically, is directed to a print data control.
2. Description of the Related Art
There are a color printing apparatus and a color printing system, capable of performing a color printing operation.
That is, for instance, an upper-grade apparatus such as a personal computer rasterizes print data constructed of characters/figures/images as multi-bits bitmap data indicated by color values of the respective primary colors, i.e., R(red), G(green), and B(blue) colors. Then, the rasterized bitmap data is transferred to a color printer control apparatus, while the bitmap data of RGB colors is directly sent or is converted into bitmap data of CMYK (cyan, magenta, yellow, black) colors corresponding to the primary colors printed by a color printer. In the color printer control apparatus, the received multi-bits bitmap data is converted into the color values of the primary colors CMYK printed by the color printer apparatus, and since the color printer control apparatus increases/decreases amounts of ink and/or toners adhered onto a printing paper in response to the color values of CMYK colors, the color printing operation is carried out. In particular, JP-A-5-83540 discloses the following techniques. That is, the black character/black line image portion is extracted from the print data in which the color image data are mixed with the black/white data such as characters and lines. While this dot is set to the maximum value of K(black) color and CMY colors (three primary colors) are set to 0, the black character black line image portion is printed out by employing only the K ink, whereas the portion other than the black character/black line image portion is printed out after the color correction process operation is carried out. As a consequence, it is possible to avoid lowering of the printing qualities, for example, color shifts and lowering of resolution.
However, the above-described printing technique does not consider lowering of the printing performance in such a case that since the print data is sent as the con-tone/multi-bits bitmap data from the upper-grade apparatus to the color printing apparatus, when the information amount of the print data is large, the data sending time is prolonged. Also, in the upper-grade apparatus, the above-explained printing technique owns such a problem that the rasterizing process time used to produce the print data is prolonged. More specifically, in a color printing apparatus and also a color printing system, which are designed to print out a large-sized page in high precision, a data amount of print data is large and thus, printing performance thereof would be lowered. In general, there are many possibilities that print documents are printed out in bi-tone/single bit, in particular, monochrome/single bit. As to color images, there are many possibilities that such a color image is contained in a portion of a document, and/or color images are contained only in several pages among a plurality of document pages. However, the above-described printing technique never considers such various use modes. Since all of these documents are print-processed as the color printing data, this printing technique requires such lengthy printing time.
Also, in the above-described printing technique, the black character/black line image is extracted by the line/image extracting circuit from the print data in which the color image such as natural images is synthesized with the single-bit black/white image data such as characters and line images. However, the black characters of the image area could not be extracted. There has also been another related application, U.S. patent application Ser. No. 09/095,889 filed Jun. 11, 1998 and entitled “Information Printing System” by E. Yoshino, et al.